Viscous dissipation and dynamics of defects in an active nematic interface ⋆ .

We consider active flow and dynamics of topological defects in an active nematic interfacial layer confined between immissible viscous fluid layers. The velocity of defects is determined by asymptotic matching of solutions in the defect core and the far field. Self-propulsion of positive defects along the direction of their "comet tails" is identified as the principal deterministic component of defect dynamics, while topological and hydrodynamic interactions among mobile defects is responsible for quasi-random jitter.